When a cell produces asexually, it produces new cells identical to the original cell. This is how all plants and animals grow, produce and replace dead or damaged cells. Their cells divide and multiply by the process of mitosis. However, some organisms also reproduce using mitosis, bacteria being a good example.
Bacteria are single–celled organisms. When the cell gets to a certain size, it splits into two, the two small cells grow and then divide again into four. This can happen very fast. Salmonella bacteria can divide once every twenty minutes if they are in warm food, by the process of Mitosis.
Mitosis is when a cell reproduces itself asexually by splitting to form two identical offspring that are called clones.
Sexual Reproduction:
Sexual reproduction involves the fusion of male and female gametes (sex cells) because there are two parents, the offspring contain a mixture of their parent’s genes. The parents have sex organs. The sex organs make sex cells. In male animals, the sex cells are called sperms. The sperms are made in sex organs called testes. In female animals, the sex cells are called eggs. The eggs are made in sex organs called ovaries. During sexual reproduction, the sperm and the egg join together. This is called fertilisation (the process of the gametes joining together). A fertilised egg or zygote is produced. The fertilised egg divides many times to form a ball of cells. Soon it will grow into an embryo and eventually it will develop into a separate individual.
The sperm is made in the testes. It has a long tail with a head at the top of it, there are millions of sperm in the testes. The head of the sperm contains enzymes. These help it to digest its way into the egg if it finds one.
The egg is much bigger than the sperm. This is because the egg contains food stores (these food stores are often called yolk) and also because the egg does not need to move actively, so it doesn’t matter if it was large and bulky.
In the nucleus of every cell in your body, there are 46 chromosomes. Chromosomes are found in the cell nucleus. They are made up of very long coils of DNA, so chromosomes also contain genes. These genes tell the cell what substances to make. They also influence all sort of other things about you, such as your sex, height, the colour of your hair, and so on.
All cells in the human body contain 46 chromosomes except for the sex cells, which contain 23 chromosomes, but when they add together they produce a zygote with 46 chromosomes but other wise the number of chromosomes remains the same.
Gametes are formed when ordinary body cells divide. A process called meiosis. It shares out the pairs of chromosomes from the diploid cell, so that the new cell will get one of each pair.
Meiosis is not a very common kind of cell division. It only happens in the reproductive organs (ovaries and testes) Meiosis produces “cells which have half the proper number of chromosomes”. Such cells are also known as “haploid gametes”. These cells are “genetically different” from each other because the genes all get shuffled up during meiosis and each gamete only gets half of them, selected at random.
Comparing Asexual Reproduction with Sexual Reproduction:
There are very few differences between sexual reproduction and asexual reproduction. They are as follows:
- Asexual reproduction is producing new cells from the parent cell, by cell division, but sexual reproduction is the fusion of the male and female sex cells.
- In asexual reproduction when new cells are formed, it is called the process of mitosis, but in fertilisation when the sperm and egg join together, a zygote is formed. It is called the process of meiosis.
- Sexual reproduction produces a baby which is not exactly like its parents, but the asexual produces an exact copy of its parent (a clone)
- Asexual reproduction produces an exact number of chromosomes.
